1. Field of the Invention
The present invention relates to a cutting machine tool monitoring method, in particular to an online real-time cutter breakage monitoring method that uses a vibration acceleration signal to monitor a cutter breakage quickly during a cutting process.
2. Description of the Related Art
Cutting is a common manufacturing procedure applied in product manufacturing for removing extra materials on a workpiece to achieve a specific geometric shape and an appropriate surface precision, so that the cutting process must be stable. High speed machining (HSM) technology with the advantages of a high production efficiency, high manufacturing precision, and high surface quality is widely used in the area of manufacturing aerospace, molding, biomedical, automobile and 3C products. However, the manufacturing process of products of these sorts must avoid unexpected abnormal cutting situations such as chatter, build-up edge (BUE) and cutter breakage which may damage the products or cause a poor surface roughness, or even affect the life of machine tools and jeopardize the safety of the operators. Therefore, shutdowns are necessary to make necessary adjustments and thus resulting in low production efficiency.
Since most key components of machine tools such as motors or controllers made in Taiwan are exported and sold to foreign countries, therefore the abnormal online diagnostic system cannot be installed into the controller directly like other foreign major manufacturers such as Okuma, and an external compatible diagnostic system is adopted instead. At present, the online diagnosis and control system generally use an external sensor as the source of measuring cutting vibrations. In addition to the problem of a low reliability of the abnormality diagnostic method, the external sensor cannot determine the source of the vibration signal. For example, a machine produces vibrations when using G00 to perform a high speed positioning, and the system may misjudge it as an abnormal cutting vibration. Therefore, systems of this sort are applicable for simple experimental cutting such as a linear cutting only, but they cannot be applied in complicated cutting process.
The causes of the cutter breakage are nothing more than a too-fast feeding, a collision, or a life exhaustion of a cutter. If a cutter breakage occurs and the machine cannot be shut down immediately to exchange the cutter, time is wasted, and manufacturing cost is increased. In an abnormal cutting analysis of a cutter breakage, a very large vibration will be produced at the moment when the cutter is broken, and this vibration will be reflected by the acceleration signal, and vibrations that follow will be close to the vibration value of an idling main shaft since the cutter is no longer in contact with the workpiece.
In view of the problems above, the inventor of the present invention provides an online real-time cutter breakage monitoring method, and uses an online cutting abnormality intellectual monitoring system of a CNC machine tool to enhance the determination speed and accuracy of the real-time cutting manufacture monitoring by using the characteristics of the abnormal cutting vibrations occurred during a cutter breakage together with the analysis of the vibration acceleration signals, so as to avoid an unnecessary shutdown or hindering the manufacturing flow.